1. Field of the Invention
This invention generally relates to a divided one-dimensional solid-state imaging device, a method of controlling a one-dimensional solid-state imaging device, and an image reading apparatus and method using the same. More particularly, this invention relates to a divided one-dimensional solid-state imaging device that is constructed by dividing photodiodes arrayed one-dimensionally in photodiode arrays of a one-dimensional solid-state imaging device such as a line CCD sensor and a line MOS type sensor into a plurality of blocks in a photodiode arraying direction; an image reading technique for photoelectrically reading an original image recorded on a photographic film or the like by the divided one-dimensional solid-state imaging device and the one-dimensional solid-state imaging device, that is, a method of controlling the divided one-dimensional solid-state imaging device and the one-dimensional solid-state imaging device for use in reading the image; and an image reading apparatus and method using the image reading technique.
2. Description of the Related Art
Conventionally, an image recorded on a photographic film (hereinafter referred to as “film”) such as a negative film and a reversal film is printed on a photosensitive material (printing paper) mainly by so-called direct exposure (analog exposure). In the direct exposure, an image on a film is projected on a photosensitive material and the surface thereof is exposed.
On the other hand, a printing apparatus that prints images by digital exposure, that is, a digital photoprinter has recently been developed which photoelectrically reads images recorded on a photographic film, converts the read images to digital signals, performs various image processing operations on the digital signals to provide image data for recording, and then scans and exposes a photosensitive material by means of a recording light modulated according to the image data to thereby record an image (latent image), which is outputted as a finished print.
Such a digital photoprinter includes as basic components a scanner (an image reading apparatus) that photoelectrically reads images recorded on a film, an image processing apparatus that performs image processing operations on the read images to obtain output image data (exposure conditions), a printer (an image recording apparatus) that scans and exposes a photosensitive material in accordance with the image data outputted from the image processing apparatus to record a latent image, and a processor (a developing apparatus) that performs developing operations on the exposed photosensitive material to output a print.
The scanner (the image reading apparatus) causes a reading light emitted from a light source to be radiated upon the film to obtain a projected light carrying a film image, focuses the projected light to form an image on an image sensor such as a CCD sensor by means of an image-formation lens and photoelectrically converts the focused light to thereby read an image, performs various image processing operations as necessity requires, and transmits the image as film image data (image data signal) to the image processing apparatus. The image processing apparatus determines the image processing conditions according to the image data read by the scanner, performs image processing operations according to the determined conditions, and transmits the resulting image data as output image data (exposure conditions) for recording an image to the printer.
If the printer is a device that scans and exposes the photosensitive material by means of a light beam; it modulates the light beam according to the image data transmitted from the image processing apparatus, deflects the light beam in a main scanning direction, and transports a photosensitive material in a sub-scanning direction perpendicular to the main scanning direction to thereby expose (print) the photosensitive material by the light beam carrying an image to form a latent image. The processor then performs processing operations such as development and the like according to the photosensitive materials to provide a print (photograph) of a reproduced film image.
Examples of image reading methods executed by the digital photoprinter are a so-called sheet reading method wherein a reading light is radiated upon the whole surface of one frame recorded on a film and the projected light is photoelectrically read by an area sensor, and a slit scan reading method wherein a line sensor is used to cause a slit-like reading light in parallel with a line sensor extending direction (main scanning direction) to radiate a film and transport the film (or move an optical system) in a sub-scanning direction perpendicular to the main scanning direction to thereby read the whole surface of the one frame. The slit scan reading method using the line sensor is more advantageous than the sheet reading method from the viewpoint of the cost because the area sensor has a number of CCD cells and photoelectric conversion elements and is therefore usually expensive, and having many CCD cells therein causes problems (e.g. the correction of defective pixels).
FIG. 8 is a schematic block diagram showing a prior art line CCD sensor.
As shown in FIG. 8, a line CCD sensor 100 is comprised of a photodiode array 102, a transfer gate 104, a transfer path 106, and an amplifier 108.
In the photodiode array 102, photodiodes PD1-PDn for storing electric charges according to the quantity of incident light for each pixel are arranged in a line from the first pixel to the nth pixel. The electric charges stored in the respective photodiodes PD of the photodiode array 102 are transmitted to the transfer path 106 via the transfer gate 104. The electric charges are then sequentially transferred on the transfer path 106 on a pixel-by-pixel basis in a direction T of an arrow in FIG. 8.
If all the n pixels are sequentially transferred and are read out by the amplifier 108 on a pixel-by-pixel basis as stated above, the time required for reading is expressed as p×n where p is the time required for transferring one pixel. The time required for reading should be reduced in order to improve the processing efficiency.
Accordingly, Japanese Patent Application Laid-Open No. Hei 5-48841 discloses a line CCD sensor in which each of photodiode arrays is divided into a plurality of sections in a scanning direction, and the respective sections connect to corresponding transfer gates, transfer paths and amplifiers so that pixels can be read out from the respective sections at a high speed.
The invention disclosed in this publication, however, is characterized by dividing the photodiodes in the scanning direction, but is not related to the method of dividing, the method of reading, or the like. It is therefore impossible to achieve the satisfactory reading efficiency by a line CCD sensor and read some types of originals at a high speed.
On the other hand, in Japanese Patent Laid-Open Publication No. 2000-69252, the assignee of the present invention has proposed an image reading apparatus that is provided with an electric charge discharge drain and an electric charge discharge gate to discharge extra electric charges and change the number of pixels to be read as necessity requires so as to eliminate the need for reading out all the pixels to thereby improve the reading efficiency.
Although the invention disclosed in this publication improves the pixel reading efficiency, a CCD itself is expensive since it must be provided with circuits and the like for discharging extra electric charges.